Dynamics of the Vegetation in the Mount Elbrus Region, USSR^∗

Abstract

Observations on the dynamics of vegetation within permanently marked plots in the Mount Elbrus region have been undertaken since 1968. Four categories of vegetation change were determined through the application of various methods, including phytocoenotic, lichenometric, and dendrochronologic. Seasonal fluctuations are most conspicuous during cold and wet vegetative periods when phenological stages are retarded by 2 to 2½ weeks, and some are totally absent. Height and thickness of grass stands decrease. Floristic compositional changes of up to 35 to 45% occur, and height and phytomass show variations of up to 100%.

Changes over 10-yr periods have a pronounced influence on phytocoenosis limits (some tens of meters) and alter the status of the codominants. Hundred-year dynamics are reflected in the limits of phytocoenosis on the order of hundreds of meters. For example, between the 8th and the 12th centuries, the altitude of the upper timberline increased by 200 to 300 m, while a lowering of similar magnitude occurred between the 13th and the 19th centuries. During the 20th century there has once more been a reversal in this trend.

Grasses and shrubs respond to climatic changes through variations in abundance and vitality, while tree species adjust their geographic limits by tens or hundreds of meters. In the event of the entire destruction of vegetation communities by exogenetic processes such as avalanches, 20 to 50 yr will be required before restoration of continuous grass cover, and 200 to 300 yr before the climax phytocoenosis is reestablished.